[ foh-tuh-peer-ee-uh-diz-uh m ]
/ ˌfoʊ təˈpɪər i əˌdɪz əm /

noun Biology.

the response, as affecting growth or reproduction, of an organism to the length of exposure to light in a 24-hour period.



How well do you know your adjectives from your adverbs? Your preposition from your pronouns? Your interjections from your conjunctions? Let’s put your knowledge of parts of speech to the text! Note: Many of the following questions will ask you to identify the parts of speech “in order.” That means the first word in all capital letters will correspond to the first option in an answer, and so on.
Question 1 of 10
In order, what parts of speech are the words in all capital letters? Alisa was VERY tired, SO she decided to go to bed.
Also called pho·to·pe·ri·o·dic·i·ty [foh-toh-peer-ee-uh-dis-i-tee] /ˌfoʊ toʊˌpɪər i əˈdɪs ɪ ti/.

Origin of photoperiodism

First recorded in 1915–20; photoperiod + -ism Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for photoperiodism

/ (ˌfəʊtəʊˈpɪərɪəˌdɪzəm) /


the response of plants and animals by behaviour, growth, etc, to photoperiods
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for photoperiodism

[ fō′tō-pîrē-ə-dĭz′əm ]


The response of an organism to changes in its photoperiod, especially as indicated by vital processes.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for photoperiodism

[ fō′tō-pîrē-ə-dĭz′əm ]

The response of an organism to changes in its photoperiod, especially as indicated by vital processes. For example, many plants exhibit photoperiodism by flowering only after being exposed to a set amount of daylight, as by requiring either a long or short day to flower. Plant growth, seed germination, and fruiting are also affected by day length. Photoperiodic responses in plants are regulated by special pigments known as phytochromes. In animals, migration, mating, amount of sleep, and other behaviors are also photoperiodic. In many animals, photoperiodism is regulated by the hormone melatonin.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.